Automatic choke valve



April 11, 1939. R. F. HOLMES ET A1.

AUTOMATIC CHOKE VALVE Filed March 25, 1935 Ob WIE- gmc/www5 Patented pr. 11,1939 l AUNITI-:o STATES' PATENT OFFICE -i AUTOMATIC CHOKE VALVE,

aussen F. Holmes ena Lester M. Crabb, mint, Mich., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application March 25, 1935, Serial No. 12,999 9 Claims. (Cl. 12S-119) 'I'his invention relates to mechanisms for au- The interior of the bellows 20 communicates tomatically regulating the position of the choke with the interior oi. the intake manifold II valve of the carburetor of an internal combusthrough a transverse bore 21 in the side wall of tion engine whenits temperature is below that the cover 22 and a vertical bore 28 which extends at which it is designed to operate. 'Ihe inventhrough the upper wall of the intake manifold II',l 5 tion resides in the provision in Asuch a mechathe wall of the body I8 and into the cover 22. In .nism of means for insuring that, as soon as the the lower enlarged end of the portion oi the bore engine starts and begins'to operate normally un- 28 which is located' in the body I8, there is der its own power, the choke valve will be opened screwed a plug-like element 29. In the upper with a combustible mixture of the proper richvided a cylindrical recess 30 into which from the ness for cold idle operation and that the choke 10We1 Surface 0f the Plug-like element there eX- voive win not be closed beyond this position while tends a relatively smell bere 3l- The recess 30 the engine is idling normally. is surrounded by a cylindrical flange 32 to which to the position at which the engine is supplied surface of the plug-like element 28, there is pro- 10 For a better understanding of the nature and there iS Secured a Combined Valve Cage and guide objects of this invention, reference is made to the 33 within which there is located a PODPet Valve following specification wherein there is described 34 Which iS nrmelly Seated 011 the upper eho- 0f the embodiment thereof which is iliustreted in the ange `by gravity and alight spring 35. the accompanying drawing. Through a bore in the center-of the valve 3l, In the accompanying drawing; there extends a pin 36 whose diameter is slightly 20 Figure 1 shows, mainly in elevation, mechaless than that of the bore and which is loosely nism in which our invention is embodied and asconnected to the upper end 0f the COmblhed Valve sociated parts of an internal combustion engine.A Cage endguide 33 S0 that it may Hutter during Figure 2 is a section through the mechanism 0Pe18tl011 0f the engine and dislodge any Dertitaken on the line 22.of Figure 3. Y cles of foreign matter which may nd their way 25 Figure 3 is a section taken on the line 3 3 inte the Smellopening between it and the bere.

of lFigure 2. To the side of the body I8 which is nearest the Figure 4 is a perspective view of two of the exhaust manifold 8l of the engine, there is seelements of the mechanism. cured abearing 38 whose inner end extends into In the drawing, the reference I8 indicates a' the 10Wel' @Omvaltment 0f the body. 0n ears 30 carburetor which is connected tothe cylinders which are formed on en intermediate Portion 0f of an internal combustion engine by a manifold the bearing, there is seated a cup-shaped hous- II. `In the carburetor Ill, there is included a ing 39 whose open end is located adjacent the butteriiy throttle valve i2 which is mounted on exhaust manifold 31 end inte whose interior the e shaft n to which en operating ann la vis se- 'outer end ef the bearing 38 extends- The cup- 35 cured and a butterily choke valve I5 which is Shaped housing 38 1S Secured t0 the hOdY I3 hy mounted oir-center on a shaft ls so that the the screws 4o which extend through theeers on iiow of air into the carburetor will tend to open it. the bearing 38 end secure the latter to the body. To the intake manifom Il adjacent the car- In the bearing there is journaled a hollow 40 buretor I0, there is secured by means of screws Shaft 4| to Whose lhholonl there ls secured en 40 'l1 e hoiiow body la which is divided into upper arm 424 The Outer end ef the erm 42 is pivotally and lower compartments by a partiti@ |9 In connected to the rod 25 which depends from the the upper compartment, there is located a metal heed of the bellows 2 ondfl'om an intermediate bellows 20 to whose open upper end there is se- Portion of tho arm there Projects a finger 43 cured a ilange 2| whose outer edge is seated on Whloh extends Parallel to andheyond the inner 45 the upper end of the body andV clamped between end of the lhollow shaft 4I. A shaft I4 extends it and the outer edge of an inverted cup-shaped through and ls Journaled the hollow Shaft 4| cover 22 by screws 23. The lower end of the and the Wall 0f the'housmg I8 ODPOSite that beuows zn is closed by e. heed 24 to which there through which the bearing 38 extends. To the is secureda rod 25 which projects into the lower end 0f the Shaft 44 Which extends through the 50 compartment of the body I8 through an opening Wall 0f the body I8 opposite that through which in the partition I8. Expansion of the bellows the bearing 38 extends, there is secured an arm 28 is limited by the partition I9 and contraction 45 whose outer end iS pivotelly Connected t0 On'e thereof is limited by a rod 28 which depends end of a rod I6. The opposite end oi the rod from the cover 22. I8 is pivotally connected to the outer end of an 55 arm 4l which is secured to the shaft I6 on which the choke valve I5 ismounted.

To the end of the hollow shaft 4I which is located Within the cup-shaped housing 39, there is secured a sector 48 in which there is provided an arcuate slot 49 in which a pin 50 is adjustably secured. To the end of the shaft 44 which is located within the cup-shaped housing 38,

there is secured the inner end of a bimetallic coil spring 5| whose outer -end engages the pin 501when its temperature is below a predetermined va ue.

To the shaft 44, between the inner end of the hollow shaft 4| and the wall of the body I8 opposite that through which the hollow shaft extends, there is secured an element 52. The element 52 is a U-shaped piece of sheet metal through whose arms the shaft 44 extends and through whose base which is made of double thickness by folding the sheet metal upon itself extends the screw 53 which secures the element to the shaft 44. On each of the arms of the element 52, there is formed a finger. The finger 54 overlies the finger 43 on the arm 42 and the linger 55 is adapted to engage the abutment 56 to limit movement of the choke valve I5 toward its closed position and to engage the abutment 51 to limit movement of the choke valve toward its open position.

When an engine on which there is installed the mechanism illustrated in the drawing and hereinbefore described is not operating. the choke during this period, the engine will be supplied with the extremely rich combustible mixture which is conducive to quick and easystarting. As soon as the engine begins to operate under its own power, the flow of air past the choke valve I5` will cause it to open partially and the ratio of fuel to air in the combustible mixture supplied to the engine will be decreased. The extent to which the choke valve opens when the engine begins to operate under its own power is dependent upon the speed of the engine and the resistance offered by the bimetallic coil spring 5I which varies inversely with the temperature of the engine, and the combustible mixture supplied to the engine at this time is, although leaner thanv it was before the engine began to operate under its own power, very rich. l

- As soon as the engine begins to operate under its own power, withdrawal of air from the inte- 'rior of the bellows 20 into the intake manifold II and, consequently, collapse of the bellows.

commences. However, because all of the air withdrawn from the bellows must pass through the small opening between the pin 36 and the bore in the valve 34, an appreciable interval of time, e. g., approximately nine (9) seconds, elapses before the bellows is completely collapsed, i. e., until the head 24 of the bellows engages the lower end of the rod 26. As the bellows is collapsed, the rod 25 is raised and the arm 42 and the hollow shaft 4I are rotated in aclockwise direction when viewed as shown in Figures 1 and 2. vThis rotation of the hollow shaft 4I causes'the sector 48 and the pin 50 to rotate in the direction-in which they are urged when the choke valve I5 moves toward its open position. Because the ow. of

air past the choke valve i5 and the weight of the linkage 45-46-41 tends to move the choke valve toward its open position, this movement of the pin 50 results in further movement of the choke valve toward its open position and effects a reduction in the richness of the combustible mixture supplied to the engine without any change in the temperature of the engine.

When the head of the bellows 20 approaches the upper limit of its movement, the rotation of the arm 42 brings the finger 43 into engagement with the nger 54 on the element 52. After the finger 43 engages the finger 54, further upward movement of the head of the bellows is positively transmitted to the shaft 44 and, therefrom, through the'arm 45, the rod 46 and the arm 41, to the choke valve I 5, with the result that by the time that the bellows has been completely collapsed, the choke valve'will have been positively opened to a predetermined position. Preferably, the position to which the choke valve is opened by the mechanism under consideration is that at which the engine will be supplied with a combustible mixture of such richness that the engine will idle properly while it is cold. Obviously, as long as the engine is idling normally, the choke valve will not be closed beyond this position.

What has been said in the next preceding paragraph is, of course, based on the assumption that the choke valve I5 has not, before the finger 43 reaches the upper limit of its movement, been opened to such an extent that the finger 54 has been moved 'beyond the upper limit of the path of the finger 43. Of course, if by the time that the head of the bellows reaches the upper limit of its movement, the choke valve has been opened to this extent, it is not desirable that the described action occur and it will not occur.

Because of its proximity to the exhaust manifold 31, the bimetallic coil spring 5I becomes heated during operation of the engine. Increase in the temperature of the bimetallic coil spring 5I causes the end thereof which engages the pin 50 to exert increasingly less pressure thereon and, consequently, as the temperature of the engine increases, the bimetallic coil spring offers less and less resistance to movement of the choke valve I5 toward its open position. Therefore.

the increase in the temperature of the engine which results from its operation will cause a gradual decrease in the richness of the 'combustible mixture supplied to the engine from the time the engine begins to operate under its own power until its temperature reaches a predetermined value when it becomes capable of operating properly upon the combustible mixture Vwith which the carburetor I is designed to supply it. When the temperature of the engine reaches this predetermined value, the outer end of the bimetallic coil spring I becomes disengaged from the pin 50 and, thereafter, the bimetallic coil spring offers no resistance to the movement of the choke Valve toward its open position. Because movement of the outer end of the bimetallic coil spring 5I in response to increase in temperature is not opposed by any externally applied forces, the bimetallic coil spring will not be injured even if it becomes heated to an excessively high temperature.

When the pressure within the intake manifold I I increases, the valve 34 will move off its seat against the resistance of the`r spring 35 and gases from the intake manifold will rush thereby into the interior of the bellows 2l!- and cause it to expand. To prevent these gases carrying into If the temperature of the engine is below a predetermined value, expansion of the bellows will, of course, through the linkage which connects its head 24 to the choke valve I5, cause the choke valve to move toward its closed position. Consequently, if, when the temperature of the engine is below a predetermined value, the throttle valve I2 is moved toward its open position or the engine tends to stall, there will be a momentary increase in the richness of the combustible mixture supplied to the engine which will insure smooth and rapid acceleration or prevent stalling of the engine. I

Obviously, the mechanism illustrated in the drawing and hereinbefore described will not affect the position of the choke valve when the temperature of the `engine on which it is installed exceeds a predetermined value.

Since, when the engine stops, the pressure within the intake manifold I I rises and the bellows 20 consequently expands and, when the temperature of the engine falls, Vthe free end of the bimetallic coil spring 5I 4moves toward the pin 50, it is apparent that, whenever the engine stops, the parts of the mechanism illustrated in the drawing and hereinbefore described automatically movef to thepositions in which they should bewhen the engine is cranked to start it.

Of course, although we have shown and described -the mechanism to which this invention relates mounted on the intake manifold of an engine with the bimetallic coil spring 5| located in juxtaposition to the exhaust manifold thereof, it will be understood that the mechanism may be mounted elsewhere on the engine and that the bimetallic coil spring maybe located in juxtaposition to any other heated part of the engine;`

We claim: i

1. In an internal combustion engine, a carburetor in which there is incorporated a choke valve,

a passage through which combustible mixture is conducted from the carburetor to the engine, an element which is movable in response to variations in the pressure within the mentioned passage andis so arranged that its Amovement in response to a decrease in the pressure within the mentioned passage tends to result in movement of the choke valve toward its open position, a yielding thermosensitive element operatively interposed between the first-mentioned element and the choke valve, and means for positively transmitting movement of the first-mentioned element 4 to-the choke valve so that the choke valve willY be positively opened to a position at which the engine will be supplied with a combustible mixengine, an element rwhich is movable in response to variations in the pressure within the passage, a hollow shaft, means whereby movement of the element is positively transmitted to the hollow shaft, a shaft journaled in the hollow shaft,

means whereby movement of the second-menltioned shaft is positively transmitted to the choke valve, a yielding thermosensltive element operatively connecting the mentioned shafts, and means on the second-mentioned shaft adapted to be engaged by the first-mentioned means after 'it has moved a predetermined distance in the direction in which it tends to move in response to a decrease in the pressure within the mentioned passage to transmit positively further movement thereof in this direction to the second-mentioned shaft so that the choke-valve will be positively opened to a position at which the engine will be supplied with a combustible mixture of such richness that it will idle properly when it is cold by the time that the firstmentioned element reaches the limit, of its movement in the direction in which it tends to move in response to a decrease in the pressure within the mentioned passage.'

3. In an internal combustion engine, a carburetor in which there is incorporated a choke valve, a passage through which combustible mixture is conducted from the carburetor to the engine, an element which is movable in response to variations in the pressure within the mentioned passage ,and is so arranged that its movement in `response to a decrease in the pressure within the mentioned passage tends kto result in but doesl not initially positively produce movement of the ment in the direction in which it tends to move in response to a decrease in the pressure within the mentioned passage.

4. In an internal combustion engine, a carburetor in which there is incQIDOrated a choke valve, a passage through which combustible mixture is conducted from the carburetor to the engine, an element which is movable in response to variations in the pressure within the passage, a hollow shaft, means whereby movement of the element is positively transmitted to the hollow shaft, a shaft journaled in the hollow shaft, means whereby movement of the second mentioned shaft is positively transmitted to the choke valve, the mentionedshafts being so arranged that movement of the element in response to a decrease in the pressure within the mentioned passage tends to result in but does not initially positivelyproduce movement of the choke valve toward its open position, and means on the second mentioned shaft adapted to be engaged by` the first mentioned means after it has moved a predetermined distance in the direction in which it tends to move in response` to a decrease in the pressure within the mentioned passage to transmit positively further movement thereof in this direction to the second mentioned shaft so that the choke valve will be positively opened to a position at which the engine will be supplied with a combustible mixture of such richness that it will` idle properly when it is cold bythe time that the first mentioned element reaches the limit of its movement in the direction in winch it tends to move in response to a decrease in the pressure within the mentioned passage.

5. In an internal combustion engine, a carburetor in which there is incorporated a choke valve, a movable element which is so arranged that its movement in one direction is consonant with movement of the choke valve toward its open position, a spring operatively interposed between the choke valve and the movable element, means for positively transmitting movement of the movable element to the choke valve so that the choke valve will be positively opened to theposition at which the engine is supplied with a combustible mixture of such richness that it will idle properly when it is cold by the time that the movable element reaches the limit of its movement in the mentioned direction without interfering with movement of the choke valve toward its open position, and means for preventing movement of the choke valve beyond its second mentioned position by the rst mentioned means.

6. In an internal mbustion engine, a carburetor in which there is incorporated a choke valve, a movable element which is designed to occupy one position when the engine is not operating and another position when the engine is operating normally under its own power, means for positively transmitting movement of the movable element to the choke valve so that the choke valve will be positively opened to the position at which the engine is*v supplied with a combustible mixture of such richness that it will idle properly when it is cold by the time the movable element reaches the last mentioned position without interfering with movement of the choke valve to- Ward its open position, and means for preventing movement of the choke valve beyond its iirst mentioned position by the first mentioned means.

'7..In an internal combustion engine, a, carburetor in which there is incorporated a choke valve, a movable element which is designed to occupy one position when the engine is not operating and another position when the engine is operating normally under itsown power so arranged that it does not interfere with movement of the choke valve toward its open position but in moving from the first to the last mentioned position may positively open the choke valve to the position at which the engine is supplied with a combustible mixture of such richness that it will idle properly when it is cold by the time the movable element reaches the last mentioned position, means for preventing positive movement of the choke valve beyond its second mentioned position by the movable element, and a thermally actuated element operatively interposed between the movable element and the choke valve.

8.In an internal combustion engine, a carburetor in which there is incorporated a choke valve, an engine actuated element which is automatically movable from one position when the engine is not operating to another position when the engine is operating normally under its own power, means for positively transmitting movement `of the engine actuated element to the choke valve so that the choke valve will be positively opened to the position at which the engine is supplied with a combustible mixture of such richness that it will idle properly when it is cold bythe time the engine actuated element re'aches the last mentioned position without interfering with movement of the choke valve toward itsopen position.

9. In an internal combustion engine, a carburetor in which there is incorporated a choke valve, an engine actuated element which is automatically movable from one position when the engine is not operating to another position when the engine is operating normally under -its own power so arranged that it does not interfere'with movement of the choke valve toward its open position but in moving from the rst to the last mentioned position may positively open the choke valve to the position at which the engine is supplied with a combustible mixture of such richness that it will idle properly when it is cold by the time the engine actuated element reaches the last mentioned position, and a thermally actuated element operatively interposed between the engine actuated element and the choke valve.

RUSSELL F. HOLMES. LESTER M. CRABB. 

